The present invention relates in general to semiconductor devices and, more particularly, to high frequency detector circuits.
In most if not all countries, the transmission of high frequency signals is controlled by industry standards and/or by government regulation. For example, transmitted signals in cellular telephones and other wireless communication devices are limited to operating in predefined frequency bands ranging from about four hundred megahertz to about 2.5 gigahertz. The amplitudes of the transmitted signals also are limited to avoid interference with other devices operating in the same or adjacent frequency bands. In addition, manufacturers extend the battery life of the wireless devices by reducing the transmitted power when such a reduction is possible without interrupting communications.
In order to control the transmitted power, a high frequency signal typically is monitored with a radio frequency (RF) detector that senses the signal's amplitude and produces a corresponding detection signal. A control circuit uses the detection signal and other communications information to control a power amplifier that produces the transmitted signal at an appropriate amplitude.
Previous systems use discrete devices such as Schottky diodes for the RF detectors. However, the discrete devices require additional circuitry to generate a useful detection signal, which increases the system's parts count as well as its size and manufacturing cost. Other systems integrate the Schottky diodes with the control circuitry to form a single integrated circuit. However, this scheme increases the complexity of the fabrication process, which increases the fabrication cost of the integrated circuit and can reduce the die yield, further increasing the cost.
Hence, there is a need for an integrated RF detector circuit and detection method that reduces the physical size and manufacturing cost of a wireless communications system.